A technique is known for synchronizing, between a camera and an electronic flash device that are connected together via wireless communication, the timing of monitor flash emission by the electronic flash device and the timing of photometry by the camera (refer to Patent Document #1). According to Patent Document #1, a master electronic flash device transmits a packet including a command for performance of monitor flash emission to a remote electronic flash device, and, upon reception of this packet, the remote electronic flash device performs monitor flash emission on the basis of a timing specified by the packet.